In my opinion, if you use old lenses with your Leica IIIF, you should shoot B&W, not only for the historical feel 😀 but also some old LTM (Leitz and FSU) lenses do get a yellow tint through the years. :bang: Perfect for B&W, just don't shoot slide in yellowed lenses (unless you have a taste for yellow).
As for the choice of colour film, I don't think it matters really much if you get you film developed a 1-hour labs. Some of these labs have digital-printing, which means your film gets developed and them film-scanned, then the image is adjusted for colour satauration, white balance, exposure... and then it is the digital file that is printed........(Once I got a B&W developed in C-41, and I got COLOURED prints 😱 , those who share the experience will know what I mean......)
For slides I like Velvia (Fuji), but sometimes the colour satauration is just to high :bang: . I am also trying the C-41 B&Ws made by Kodak, since I don't have a dark room and developing Neopan is getting expensive. Anyone have experience with the Kodak C-41 B&Ws??